Zillow is a good tool to look for trends and interesting locations.
It is a bad tool to use for actively shopping as many have offers by the time Zillow posts them.
I do it all the time. I like Redfin better but they don’t cover everywhere.
This.
I do the shopping at tax sales, auctions, and from fsbo signs on properties. Rarely do I see anything remotely desirable for my purposes, online.
As for selling online, Zillow isn't user friendly imo. I'd rather go with craigslist (free) or ebay (fee).
There are more eyeballs on Zillow, and I know plenty of people who find it agreeable for selling, but I just don't. Too many hoops to jump through, and you have to keep an eye on it or your photos go poof, maybe the entire listing too.
Besides, the quantity of viewers isn't always a benefit. I tend to target regions, so craigslist is preferred.
Still, I do this a lot and if you have a single property for rental, I'd recommend local resources -- newspapers, community-focused online groups, etc., even in a major city. The market consists largely of people already nearby.